tRESTClient properties

Component family

ESB/REST

Function

The tRESTClient component sends
HTTP and HTTPS requests to a REpresentational State Transfer (REST)
Web service provider and gets the corresponding responses. This
component integrates well with Talend Runtime to get HTTPS support, with more
QoS features to be supported in time.

Purpose

The tRESTClient component is used
to interact with RESTful Web service providers by sending HTTP and
HTTPS requests using CXF (JAX-RS).

Basic settings

URL

Type in the URL address of the REST server to be invoked. When the
Use Service Locator check box
is selected, this field will not show and the URL of the REST server
will be obtained from the Service Locator server
automatically.

Relative Path

Enter the relative path of the REST server to be invoked.

For example, if you want to access
http://localhost:8888/services/Customers/list:

If Use Service Locator is
disabled: You can enter any of the first part of the address in the
URL field, and the second part
in the Relative Path field. For
example, you can enter http://localhost:8888 in
URL and
/services/Customers/list in Relative Path. You can also enter the full path of
the REST server in URL and leave
Relative Path blank.

If Use Service Locator is
enabled: The URL part will be given
by the Service Locator. In this case, you need to know the URL part, and specify the rest part in
Relative Path. This depends on
the service you request. For example, on tRESTRequest, you specify REST
Endpoint as
http://localhost:8888/services and enable Use Service Locator. Then, if you want to
use this service, on tRESTClient
side, you should specify /customers/list in Relative
Path.

HTTP Method

From this list, select an HTTP method that describes the desired
action. The specific meanings of the HTTP methods are subject to
definitions of your Web service provider. Listed below are the
generally accepted HTTP method definitions:

- GET: retrieves data from the
server end based on the given parameters.

- POST: uploads data to the server
end based on the given parameters.

- PUT: updates data based on the
given parameters, or if the data does not exist, creates it.

- PATCH: modifies data partially
based on the given parameters.

- DELETE: removes data based on the
given parameters.

Content Type

Select XML, JSON, or FORM
according to the media type of the content to be uploaded to the
server end.

This list appears only when you select the POST,
PUT, or PATCH HTTP method.

Accept Type

Select the media type the client end is prepared to accept for the
response from the server end.

Available options are XML,
JSON, and ANY. When ANY is
selected, the response message can be of any type and will be
transformed into a string.

Query parameters

Specify the URI query parameters in the form of name-value pairs.

This option is mostly used with the GET method.

Schema and Edit
Schema

A schema is a row description, it defines the number of fields
that will be processed and passed on to the next component.

This component uses three built-in, read-only schemas.

Click Edit Schema to view the
schema structure.

Warning

Changing the schema type may result in loss of the
schema structure and therefore failure of the
component.

Input Schema

Schema for the input data. This schema contains two
columns:

- body: stores the content of
structured input data

- string: stores the input
content when it is, or is handled as, a string.

Response Schema

Schema for server response. This schema is passed onto the next
component via a Row > Response link, and it contains three
columns:

- statusCode: stores the HTTP
status code from the server end.

- body: stores the content of a
structured response from the server end.

- string: stores the response
content from the server end when it is, or is handled as, a string.

Error Schema

Schema for error information. This schema is passed onto the next
component via a Row > Error link, and it contains two
columns:

- errorCode: stores the HTTP
status code from the server end when an error occurs during the
invocation process. The specific meanings of the errors codes are
subject to definitions of your Web service provider. For reference
information, visit en.wikipedia.org/wiki/List_of_HTTP_status_codes.

Select this check box to enable the Service Locator. It
maintains the availability of the service to help meet demands and
service level agreements (SLAs). Specify the Service namespace and the
Service name in the corresponding fields.

Use Service Activity Monitor

Select this check box to enable the Service Activity
Monitor. It captures events and stores this information to facilitate
in-depth analysis of service activity and track-and-trace of messages
throughout a business transaction. This can be used to analyze service
response times, identify traffic patterns, perform root cause analysis
and more.

Use Authentication

Select this check box if authentication is required on the REST server end. Select from
Basic HTTP, HTTP Digest, SAML
Token (ESB runtime only), and OAuth2 Bearer in the list. Authentication with the
SAML Token works in runtime
only.

If you use Basic HTTP, HTTP
Digest, or SAML Token (ESB
runtime only), you need to provide your username and
password.

To enter the password, click the [...] button next to the
password field, and then in the pop-up dialog box enter the password between double quotes
and click OK to save the settings.

If you use OAuth2 Bearer, you
need to fill the Bearer Token field
with a base64-encoded credential string.

Use Authorization

Select this check box to enable authorized call. Specify the
client's role in the Role field.
This option appears when SAML Token (ESB
runtime only) is selected in the Use Authentication list.

For more information about the management of user roles and
rights, see the Talend Administration Center User Guide and Talend ESB Infrastructure Services Configuration
Guide.

Use Business Correlation

Select this check box to create a correlation ID in this
component.

You can specify a correlation ID in the Correlation Value field. In this case the
correlation ID will be passed on to the service it calls so that
chained service calls will be grouped under this correlation ID. If
you leave this field empty, this value will be generated
automatically at runtime.

When this option is enabled, tRESTClient will also extract the correlation ID
from the response header and store it in the component variable for
further use in the flow.

Die on error

This check box is selected to kill the Job when an error
occurs. Clear the check box to skip the row on error and complete the
process for error-free rows.

Advanced settings

Log messages

Select this check box to log the message exchange between the
service provider and the consumer.

Convert Response To DOM Document

Select this check box to convert the response from the server to
document type.

Clear this check box if you want the response to be handled as a
string.

Drop JSON Request Root

This option appears when HTTP Method is POST, PUT or PATCH and
Content Type is JSON. Select this check box to drop root
JSON elements.

Wrap JSON Response

This option appears and is enabled by default when JSON is selected from the Accept Type list in the Basic settings view.

With this check box selected, the response is wrapped with a
root element. Clear this
check box to remove the root
element from the response.

HTTP Headers

Type in the name-value pair(s) for HTTP headers to define the
parameters of the requested HTTP operation.

This option appears when HTTP Method is POST, PUT or PATCH.
Select this check box to disable encoding the payload as
chunks.

Service Locator Customer Properties

This option appears when Use
Service Locator is enabled in the Basic settings tab. Click [+] to add as many properties as needed to the table.
Enter the name and the value of each property in the Property Name field and the Property Value field respectively to identify
the service.

Service Activity Customer Properties

This option appears when Use
Service Activity Monitor is enabled in the Basic settings tab. Click [+] to add as many properties as needed to
the table. Enter the name and the value of each property in the
Property Name field and the
Property Value field respectively
to identify the service.

Connection timeout

Set the amount of time, in seconds, that the client will attempt
to establish a connection before it times out. If set to 0, the client will continue to attempt
to open a connection indefinitely. (default: 30)

Receive timeout

Set the amount of time, in seconds, that the client will
wait for a response before it times out. If set to 0, the client will wait indefinitely.
(default: 60)

Use HTTP proxy

Select this check box if you are using a proxy server.
Once selected, you need to provide the connection details: host, port,
username and password.

tStatCatcher Statistics

Select this check box to gather the Job processing
metadata at the Job level as well as at each component level.

Dynamic settings

Click the [+] button to add a row in the table and fill
the Code field with a context variable to turn on or off
the Use Authentication or Use HTTP
proxy option dynamically at runtime. You can add two rows in the table to set
both options.

Once a dynamic parameter is defined, the corresponding option becomes highlighted and
unusable in the Basic settings view or Advanced settings view.

This component is used as a RESTful Web service client to
communicate with a RESTful service provider, with the ability to
input a request to a service into a Job and return the Job result as
a service response. Depending on the actions to perform, it usually
works as a start or middle component in a Job or subjob.

Connections

Outgoing links:

Row: Response; Error.

Trigger: On Subjob Ok; On Subjob
Error; Run if; On Component Ok; On Component Error.

Incoming links:

Row: Main; Reject.

Trigger: Run if; On Subjob Ok; On
Subjob Error; On component Ok; On Component Error.

For further information regarding connections, see Talend Studio User
Guide.

Global Variables

NB_LINE: the number of rows processed. This is an After
variable and it returns an integer.

HEADERS: the HTTP response headers. This is a Flow
variable and it returns a list of HTTP response header values.

CORRELATION_ID: the correlation ID by which chained
service calls will be grouped. This is a Flow variable and it returns a string.

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space to access the variable list and choose the variable to use from it.

For further information about variables, see Talend StudioUser Guide.

Limitation

n/a

Scenario 1: Getting user information by interacting with a RESTful service

This scenario describes a three-component Job that retrieves user information based on
the user ID from a REST service via HTTP GET and displays the retreived user
information, as well as the message exchange between the client and the server, on the
Run console.

If you are not a Talend ESB user, then you need
to get from your REST service provider the URL, the data structure, and the required
parameters of the REST service you are going to call and make necessary modifications in
the scenario configurations accordingly.

Setting up the Job

Drop the following components from the Palette onto the design workspace:

tRESTClient, used to call the
REST service and retrieve user information from the server
end,

tXMLMap, used to adapt the tree
structure of the REST service, and

tLogRow, to display the retrieved
user information on the Run
console.

Connect the tRESTClient to the tXMLMap using a Row > Response
connection.

Connect the tXMLMap to the tLogRow using a Row > Main connection, and
give it a name, out in this
example.

Label the components to best describe the actions to perform.

Configuring the components

Configuring the service call

Double-click the tRESTClient component to
open its Basic settings view.

Fill the URL field with the URL of the
REST service you are going to invoke, "http://localhost:8088/users" in this example. Note that the
URL provided in this use case is for demonstration purposes only and not a
live address.

From the HTTP Method list, select
GET to send an HTTP request for
retrieving the existing records.

From the Accept Type list, select the
type the client end is prepared to accept for the response from the server
end, XML. Leave the rest of the settings as
they are.

Click the [+] button beneath the
Query parameters table to add two
parameters, from and to, and set both parameters to 2, to get the information of the user with the
ID of 2.

Alternatively, you can query the information of the user with the ID of 2
by adding ?from=2&to=2 to the service
URL.

In the Advanced settings view of the
tRESTClient component, select the
Log messages and the Convert Response To DOM Document check boxes to
log the message exchange to the server and convert the response from the
server to document type.

Mapping the service structure and displaying the retrieved user
information

Double-click the tXMLMap component to
open the Map Editor.

If you selected XML in the Accept Type list of the tRESTClient component, define the input XML tree structure
according to the service structure.

In the input table, right-click the default root node of the body column, select Rename from the contextual menu, and
rename it to users.

Right-click the users node,
select Create Sub-Element from the
contextual menu, and create sub-element named user. Set user as the loop element because the XML structure
of the Web service to be invoked is looped on this element.

Right-click the user node,
select Create Attribute from the
contextual menu, and enter id in
the [Create New Attribute] dialog
box to create an attribute named id for the user
node.

Right-click the user node
again, select Create Sub-Element
from the contextual menu, and enter first_name in the [Create New
Element] dialog box to create an sub-element named
first_name for the user node.

Repeat this operation to create another sub-element under the
user node, last_name.

Drop the id, first_name and last_name columns from the input table to the output
table, and then click OK to
validate the mapping and close the Map Editor.

If you selected JSON in the Accept Type list of the tRESTClient component, the response from the server end will
be sent back in JSON format and converted to document type. In this example,
the converted response structure looks like the following:

Note that the <root> element is removed if the Wrap JSON Response check box is cleared in the
Advanced settings of the tRESTClient component.

Define the input XML tree structure accordingly and map it with the output
data flow in a similar manner as described above.

Double-click the tLogRow component to
open its Basic settings view.

Click the Sync columns button to make
sure the component schema is synchronized with the output schema of the
tXMLMap component.

In the Mode field, select the Table option to display the GET result in table
cells.

Saving and executing the Job

Press Ctrl+S to save your Job.

Press F6 or click Run on the Run console to
launch the Job.

The console shows that the tRESTClient
component successfully reads the user information from the server end
corresponding to the specified user ID.

If you selected XML in the Accept Type list of the tRESTClient component, the execution result will be:

If you selected JSON in the Accept Type list of the tRESTClient component, the execution result will be:

Scenario 2: Updating user information by interacting with a RESTful service

This scenario describes a three-component Job that updates the information of a list
of users to a remote database through a REST service using the HTTP POST method. When
executed, the Job displays the client-server message exchange information on the
Run console.

The user information to be updated to the server is stored in a CSV file, which looks
like the following:

If you are a Talend ESB user, create a Job
as described in Scenario 3: REST service accepting HTTP POST requests and run the Job
as a REST server to expose a REST service that accepts HTTP POST requests. Upon
execution of the Job, the console displays the service implementation information,
including the service endpoint URL, which is http://localhost:8045/users in
this example. If you enter http://localhost:8045/users?_wadl in your Web
browser, you should see the service definition information like the following:

If you are not a Talend ESB user, then you need
to get the service-related information from your REST service provider including the
URL, the resource path, and the data structure, and make necessary modifications in the
scenario configurations accordingly.

Setting up the Job

Create a Job and add the following components by typing their names in the
design workspace or drop them from the Palette:

tFileInputDelimited, to read user
information of a local file,

tXMLMap, to adapt the input
structure to the REST service structure, and

tRESTClient, used to call the
REST service to send data to the remote database.

Connect the tFileInputDelimited to the
tXMLMap using a Row > Main
connection.

Connect the tXMLMap to the tRESTClient using a Row > Main connection, and
give the output flow a name, request in
this example.

Label the components to best describe the actions to perform.

Configuring the components

Configuring the input data and the structure mappings

Double-click the tFileInputDelimited
component to open its Basic settings
view.

Specify the input file in the File name
field, fill the Header field with 1 to skip
the header row, and keep the rest parameters as they are.

Click the [...] button next to Edit schema to open the [Schema] dialog box, and edit the input schema as
follows:

id, type Integer, 2 characters
long, set as the key column

first_name, type String

last_name, type String

Double-click the tXMLMap component to
open the Map Editor.

Rename the root node in the output
table: right-click the node, select Rename
from the contextual menu, and specify a new name in the pop-up dialog box,
user in this example.

Select all the three columns in the input table and drop them onto the
user node, and select the Create as sub-element of target node option from
the pop-up dialog box to set these columns as sub-elements of the user node. When done, click OK to validate the mappings and close the Map
Editor.

Configuring the service call

Double-click the tRESTClient component to
open its Basic settings view.

Fill the URL field with the URI location
where the REST service is accessible,
"http://localhost:8088/users" in this example.

In the Relative Path field, enter the
resource path, "/post/" + row1.id+ "/" + row1.first_name + "/" +
row1.last_name in this example. This will send the data from the
input row to the server end via the resource path.

From the HTTP Method list, select
GET to send an HTTP request for
retrieving the existing records.

From the Accept Type list, select the
type the client end is prepared to accept for the response from the server
end, XML.

In the Advanced settings view of the
tRESTClient component, select the
Log messages check box to log the
message exchange information with the server.

Leave the rest of the settings as they are.

Running the Job and checking the result

Press Ctrl+S to save your Job, and press
F6 to execute it.

The console displays the client-server exchange information:

The console of the server Job displays the exchange information and the database
update result.